Open Access Thesis
In Iowa, the most troublesome sedges to identify are Carex brevior, C. festucacea, C. molesta, C. normalis, C. tenera, and C. tenera var. echinodes. These taxa form the C. brevior group--part of an even larger aggregate of species associated with C. straminea. Their morphological features are indistinct and intergrade into one another. Botanists have had difficulty classifying members of this aggregate for nearly 200 years. Some authors have viewed the taxa as separate species, others as polymorphic forms of a single species. Much of the contention has centered upon the variation of taxonomic characters used to delimit and distinguish species.
The objectives of my study were: 1) to randomly sample up to 30 specimens from each population, at several populations of each taxa, to obtain statistical parameters for morphological characters and ascertain if variation occurs within populations, between populations, and between taxa; 2) to evaluate 44 characters and 12 character ratios for each taxa by Univariate Analysis and Stepwise Discriminant Analysis (SDA) and obtain reliable taxonomic characters or character combinations; and 3) to test the validity of taxonomic classifications within the C. brevior group by determining if the morphological forms are significantly different using Canonical Discriminant Analysis (CDA).
There were 450 samples collected at 15 sites (21 populations). The taxa were mostly found in different micro-habitats. Most character means were significantly different (p < 0.0001), e.g., means of C. molesta and C. brevior were significantly different for 52 of the 56 characters tested. However, single characters could not reliably separate taxa because of overlapping ranges of variation. CDA revealed taxa to be significantly different (F = 24.08; p < 0.0001) along 4 canonical axes. SDA identified character combinations or suites which could reliably delimit and distinguish taxa. There were no subgroups observed within the taxa. Most of the variation expressed by each taxon was found within populations and there were few differences between populations. The characters varied in predictable patterns and this variation is mostly attributed to phenotypic plasticity. However, specimens were found at sympatric sites with unusual character states or mixed character suites, suggesting they are putative hybrids.
Year of Submission
Master of Arts
Department of Biology
Tallgrass Prairie Center
Lawrence J. Eilers, Chair
1 PDF file (xiii, 134 pages)
©1991 Scott C. Zager
Zager, Scott C., "Multivariate analysis of the Carex brevior group in Iowa" (1991). Dissertations and Theses @ UNI. 181.